Due to changes to a file inside wsusscn2.cab (since 2014-08-27) WSUS Offline Update isn't able to dynamically determine superseded updates anymore. This will cause it to redownload superseded updates once.

.\doc\history.txt wrote:- NOTE: Please delete ...\exclude\ExcludeList-superseded.txt once you updated to v. 9.4 to be sure to have it re-created during the next download run...- Fix: Superseded updates' determination was broken by new wsusscn2.cab catalog file format (Thanks to "boco", "aker" and "wyoming")...